Palestinians are warning that the failure of a coming Middle East peace conference, convened by the US, could undermine chances of a two-state solution and may threaten a return to violence.

Ehud Olmert, Israel's prime minister, reiterated after talks with Gordon Brown in London yesterday that the conference, scheduled for Annapolis, Maryland, next month, would focus on core issues rather than detailed negotiations, fuelling fears that it carries unacceptably high risks.

"We can live without a conference but we can't live with a conference that fails," said a close adviser to the Palestinian president and Fatah leader, Mahmoud Abbas. "It will be good not just for Hamas, but for al-Qaida too." Hamas, the Islamist movement in control of the Gaza Strip, says the conference is an American-Israeli trap.

Mustafa Barghouti, a former Palestinian information minister, said Mr Abbas would be badly hit by failure. "Fatah will be very much weakened," he said. "It would have a very serious impact. But at the same time it would reveal the fact that without a real international conference the Arabs need a different strategy."

Privately diplomats say they doubt the conference can produce a positive result and fear the consequences if it does not. "It would be a disappointment not to have a conference but failure would be a disaster for the Palestinians and everyone else," one official said. "I am not sure Abbas and Salam Fayyad [Palestinian prime minister] will be able to survive it."

Mr Brown hinted yesterday that he shared these concerns. "We are not complacent about the outcome," he said. "We do not have false hopes but we do believe it's an important step forward."

Mr Olmert also underlined Israel's opposition to Hamas, which he dismissed as a "terrorist organisation", whose members would not be freed from prison. Israel reported that four Qassam rockets fired from Gaza landed in the western Negev region yesterday but caused no damage or injuries. Later an Israeli aircraft attacked a car in central Gaza, killing a senior Hamas security official.

Condoleezza Rice, the US secretary of state, has made six trips to the region this year to broker an agreement, but a timetable for an independent Palestinian state is still elusive. "No one can seriously expect that within this short span of time between now and the end of November we can achieve what we haven't been doing in the last 40 years," Mr Olmert added.

In recent weeks, Mr Olmert has floated the idea of a division of authority in Jerusalem, but there has been no agreement on this. At the same time the Israeli army has said it will expropriate land from four Palestinian villages between Jerusalem and Jericho in the occupied West Bank.

"Even if an agreement is reached about a declaration it will be nothing but another paper," said Mr Barghouti. "The trick is to get not another piece of paper but the implementation of a real peace deal."

Wider participation in the conference is an open question. Syria is unlikely to attend; Saudi Arabia has sent mixed signals. Jordan and Egypt will be there. But Hosni Mubarak, Egypt's president, warned this week: "The region cannot sustain a fresh failure of peace efforts."

"Nothing about this conference looks right," said Yossi Alpher, an Israeli analyst. "Everything points to a failure foretold. The only real issues that remain to be resolved are, first, whether the conference will be held at all and second, regardless of whether or not it ... takes place, how bad the damage it generates will be."

A bad outcome at Annapolis could have other ramifications. Tony Blair, representative of the quartet of Middle East peacemakers, is planning a donors' conference in December to raise cash for a viable Palestinian state. It is hard to see that effort succeeding if there is not a clear "political horizon" to look forward to.